Intelligent Reflecting Surfaces for Secure 6G Wireless Communications

Abstract

The dissertation thesis deals with the topic of intelligent reflecting surfaces (IRS) and physical layer security in wireless communication systems. The main goal is to improve the spectrum efficiency and the performance of the Sixth Generation (6G) mobile networks by using intelligent surfaces that reflect the transmission signals in non-orthogonal multiple access (NOMA) networks. This thesis exploits the physical layer security characteristics, improves the capacity of a NOMA network, and the efficiency of the application of the IRS to mitigate the adverse effects of fading, shadowing, and finally also transmission environments in satellite networks.

The thesis introduces a new approach for improving the capacity of a NOMA network by using the Aerial IRS, the satellite networks's performance by increasing the number of phase shifters of the IRS to mitigate the adverse effects of fading, shadowing, and transmission environments, and the understanding of how the meta-surfaces in IRS can improve the power allocation and transmission performance in the NOMA network. The dissertation thoroughly examined three specific use cases: (1) physical layer security in IRS-based downlink and uplink NOMA networks, (2) capacity enhancement of NOMA networks through multiple aerial intelligent reflecting surfaces, and (3) the secrecy performance of IRS-assisted satellite networks. In the dissertation, closed-form analytical formulations for performance metrics, including Outage Probability (OP), Secret Outage Probability (SOP), Ergodic Capacity (EC), average throughput, and energy consumption were derived and rigorously validated through simulations.

The outcomes of the dissertation demonstrated advancements in network security and efficiency of transmission. Simulations showcased improvements in scalability and throughput compared to state-of-the-art solutions, and the dissertation represents a promising approach for 6G network optimization and secure communication. The dissertation thesis includes a commented collection of published papers related to the main research goals.